1. Field Of The Invention
This invention relates generally to the production of permanent magnetic sinter bodies.
2. Description Of The Prior Art
The binary alloys of the type LnCo.sub.5, wherein Ln represents a lanthanoid, possess excellent characteristics as permanent magnets. These materials are generally characterized by extremely high remanence, high coercive force and high maximum energy product (BH).sub.max, and they exhibit a generally linear demagnetization curve (Sci. Am. December, 1970, pp. 92).
The binary alloy permanent magnets, however, are quite expensive, both in terms of cost of materials and in terms of cost of production, and they possess the undesirable characteristic of exhibiting a relatively high irreversible temperature coefficient at temperatures of above 250.degree. C. These deficiencies are particularly applicable to the binary alloy SmCo.sub.5, which in general has been recognized as possessing the most superior characteristics of the binary alloys.
Recent efforts directed to the development of alternative materials, in which samarium is completely or partly substituted with cheaper members of the lanthanoid series (see Martin-Benz, General Electric R & D Center, Schenectady, N.Y., Report No. 70-C-261, August, 1970), has revealed that ternary alloys, formed by substituting a less expensive lanthanoid element for the more expensive samarium, will possess better magnetic characteristics than those of the binary component of lesser magnetic qualities. For instance, it was found that Sm.sub.0.5 Pr.sub.0.5 Co.sub.5 possesses better magnetic characteristics than PrCo.sub.5.
Moreover, preliminary evidence suggests that the temperature coefficient of magnetization may be considerably reduced by appropriate selection of the lanthanoid elements used in the ternary alloy. It has also been recently demonstrated that exceptionally good coercive force can be obtained by using selected ternary alloys.
The desirability of the ternary lanthanoid-lanthanoid-cobalt alloys, is therefore well established. The procedures for preparing permanent magnetic sinter bodies of such alloys, however, has proven to be industrially unsatisfactory. In Martin-Benz, Supra., for instance, it is suggested to prepare these alloys by first mixing the elements in selected ratios, effecting alloying by metallurgical smelting, and then sintering the alloy. This technique, however, is particularly costly, especially if, as in many instances, it becomes necessary to vary the ratios of the ternary elements from batch to batch.
A need exists, therefore, for a technique of preparing ternary lanthanoid-lanthanoid-cobalt permanent magnetic sinter bodies in a more industrially advantageous manner.